Embodiments of the invention relate generally to a manufacturing method, which is used to manufacture high melting point metal based objects. Here, the “high melting point metal” related to a kind of metal whose melting point is higher than 2500 degrees Celsius, such as molybdenum, tungsten, tantalum, or their alloys.
Three-dimensional (3D) objects such as collimators used in x-ray imaging devices can be manufactured by using laser rapid manufacturing technology. One laser rapid manufacturing approach uses a laser beam to scan across and selectively sinter/melt metal powder to build up a prototype layer-by-layer from a predetermined model of the 3D object. Laser sintering/melting is a process in which the temperature of a powdered material is raised to its melting/softening point by thermal heating with a laser beam, thereby causing the particles of the powder to fuse together in the heated region.
However, if the melting point of the powdered material is very high, such as tungsten (about 3410 degrees Celsius), it may not melt the powdered material completely through the normal laser. To solve this problem, one conventional method may use a high power laser to manufacture the 3D objects. But, the high power laser will require significant energy input during the manufacturing process which may increase the costs.
Another conventional method may use low melting point binders, for example including nonmetallic binders such as nylon and silicate and metallic binders such as iron and nickel, to add into the high melting point metal or alloys to improve the forming capability for manufacturing. For example, nickel is used as a binder for tungsten to manufacture collimators through laser cladding. However, when the nickel content in the powder mixture is low (for example, lower than 50 vol %), the powder mixture also has a poor forming capability. When the nickel content in the powder mixture is high (for example, higher than 50 vol %) to ensure forming capability for manufacturing by laser cladding, the collimator may be deficient in its absorbing capability.
For these and other reasons, there is a need for manufacturing 3D objects which are made of high melting point metal without binders or only with low proportion of binders.